No. You cannot record 4k videos but you can play 4k videos on Honor 8.
Basis on my extensive use of Honor 8 for about 4 months, I can say that these are the biggest advantages of Honor 8.
01) Super Aesthetics
02) Superb Camera Quality
03) Good Internal Software
No. Honor 8 do not have FM Radio.
Yes, Honor 8 does have IR sensor. You can use it as IR remote control with most of appliances, which support basic IR reception.